G gallery, several parallel drifts e.g. the crosscuts in sublevel caving. gallery head, drift (tunnel) which will act as a main drift for several parallel drifts laying

perpendicular or at an angle to the gallery head. galvanic action, physical-chemical process characterized by the flow of a current caused

when dissimilar metals contact each other or through a conductive medium. This action may create sufficient voltage to cause premature firing of an electric blasting circuit, particularly in the presence of salt water. Konya and Walter, 1990.